Lab case 429 interpretation

Question 1:

PH = 7.31, that is mild acidaemia

PCO2 is high (51 mmHg). So we have respiratory acidosis. We don’t have enough information to decide if it is acute or chronic

HCO3 is 21 mmol/L, that is low. So we have metabolic acidosis. Because we have metabolic acidosis then we need to calculate the ANION GAP. That is: [Na – (Cl + HCO3)] = 12. Accordingly, the metabolic acidosis is NAGMA.

So we have mixed NAGMA and respiratory acidosis.

Other abnormal findings:

The most striking abnormal finding is the very high BSL level = 52 mmol/L. Next, we need to calculate the plasma osmolarity and the corrected Na level.

Plasma osmolarity = Na x 2 + Glucose + Urea = 130 x 2 + 52 + 23 = 335 ( hyperosmolar).

Next we need to calculate the corrected Na level for hyperglycemia. The equation that we use is: Corrected Na = measured Na + (Glucose-5)/3 = 133 + (52-5)/3 = 148.6 (Mild hypernatraemia).


Next we need to calculate the expected water deficit. The equation that we use is: 0.6 x premorbid weight x (1 – 140/corrected Na) – This lady was about 80 kg – Accordingly, the expected water deficit will be  2.88 L. – The usual water deficit in HHS is 6-9 L.

Other abnormal findings are elevated urea and creatinine, we can use these 2 levels to calculate the Urea-Creatinine ratio. The equation that we use for that is Urea x 1000/ Cr.

In this case the ratio will be: 23 x 1000/ 154 = 149 ( Pre-renal renal failure / dehydration).

Lactate is elevate (4.1), likely due to reduced tissue perfusion secondary to dehydration.

Question 2:

First step in the management of HHS is to check the ketones level. if the ketones level is 3 or more then treat the patient as DKA (the patient needs more insulin).

The principles of HHS management are:

To vigorously rehydrate the patient while maintaining electrolyte balance, replace the fluid deficit over 24 hours

Correct hyperglycemia

Treat the underlying condition

Monitor CVS, respiratory system, renal function and CNS function.

Avoid complication of aggressive rehydration

The goal of the initial therapy is to restore the intravascular and extravascular volume and to restore peripheral perfusion. As the majority of electrolyte losses are Na, Cl and K, the base fluid that should be used is 0.9% sodium chloride solution with potassium added as required.

If ketones level is more than 1, then we need to start insulin therapy. The dose that is recommended is 0.05 unit per hour. We need to monitor BSL closely and avoid sudden massive drop in blood glucose level (Lead to sudden drop in osmolarity and cerebral oedema).

If ketones level is more than 3, then the recommended starting dose of insulin is 0.1 unit per Kg body weight.


The patient needs to be monitored closely, preferably in resuscitation bed and to be admitted to HDU.